The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Recent increases in oil prices lead vehicle companies into more competition to improve fuel efficiency of vehicles. Especially in regards to the engine of a vehicle, research has focused on weight reduction through downsizing and improvement in fuel efficiency.
As an approach to improving fuel efficiency in regard to a vehicle transmission, there is a method of increasing the number of gears, which aims at operation of an engine at a desired operation point, ultimately leading to improvement in fuel efficiency.
A multistage transmission also enables an engine to operate at slow speed, i.e., at a relatively low RPM (revolutions per minute) range, so as to improve noise and vibration characteristics of a vehicle.
However, as the number of gears increases, the number of parts constituting the transmission correspondingly increases. This deteriorates mountability and overall transmission efficiency and also increases raw material costs and weight of the transmission. Therefore, we have discovered that in order to improve fuel efficiency through increasing the number of gears of a transmission, it is a key to devise a multistage transmission with reduced number of parts and having a simple structure.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.